module ReamazeAPI
  module Utils
    module HashKeys
      refine ::Hash do
        # Returns a new hash with all keys converted using the +block+ operation.
        #
        #  hash = { name: 'Rob', age: '28' }
        #
        #  hash.transform_keys { |key| key.to_s.upcase } # => {"NAME"=>"Rob", "AGE"=>"28"}
        #
        # If you do not provide a +block+, it will return an Enumerator
        # for chaining with other methods:
        #
        #  hash.transform_keys.with_index { |k, i| [k, i].join } # => {"name0"=>"Rob", "age1"=>"28"}
        def transform_keys
          return enum_for(:transform_keys) { size } unless block_given?
          result = {}
          each_key do |key|
            result[yield(key)] = self[key]
          end
          result
        end

        # Destructively converts all keys using the +block+ operations.
        # Same as +transform_keys+ but modifies +self+.
        def transform_keys!
          return enum_for(:transform_keys!) { size } unless block_given?
          keys.each do |key|
            self[yield(key)] = delete(key)
          end
          self
        end

        # Returns a new hash with all keys converted to strings.
        #
        #   hash = { name: 'Rob', age: '28' }
        #
        #   hash.stringify_keys
        #   # => {"name"=>"Rob", "age"=>"28"}
        def stringify_keys
          transform_keys(&:to_s)
        end

        # Destructively converts all keys to strings. Same as
        # +stringify_keys+, but modifies +self+.
        def stringify_keys!
          transform_keys!(&:to_s)
        end

        # Returns a new hash with all keys converted to symbols, as long as
        # they respond to +to_sym+.
        #
        #   hash = { 'name' => 'Rob', 'age' => '28' }
        #
        #   hash.symbolize_keys
        #   # => {:name=>"Rob", :age=>"28"}
        def symbolize_keys
          transform_keys{ |key| key.to_sym rescue key }
        end
        alias_method :to_options,  :symbolize_keys

        # Destructively converts all keys to symbols, as long as they respond
        # to +to_sym+. Same as +symbolize_keys+, but modifies +self+.
        def symbolize_keys!
          transform_keys!{ |key| key.to_sym rescue key }
        end
        alias_method :to_options!, :symbolize_keys!

        # Validates all keys in a hash match <tt>*valid_keys</tt>, raising
        # +ArgumentError+ on a mismatch.
        #
        # Note that keys are treated differently than HashWithIndifferentAccess,
        # meaning that string and symbol keys will not match.
        #
        #   { name: 'Rob', years: '28' }.assert_valid_keys(:name, :age) # => raises "ArgumentError: Unknown key: :years. Valid keys are: :name, :age"
        #   { name: 'Rob', age: '28' }.assert_valid_keys('name', 'age') # => raises "ArgumentError: Unknown key: :name. Valid keys are: 'name', 'age'"
        #   { name: 'Rob', age: '28' }.assert_valid_keys(:name, :age)   # => passes, raises nothing
        def assert_valid_keys(*valid_keys)
          valid_keys.flatten!
          each_key do |k|
            unless valid_keys.include?(k)
              raise ArgumentError.new("Unknown key: #{k.inspect}. Valid keys are: #{valid_keys.map(&:inspect).join(', ')}")
            end
          end
        end

        # Returns a new hash with all keys converted by the block operation.
        # This includes the keys from the root hash and from all
        # nested hashes and arrays.
        #
        #  hash = { person: { name: 'Rob', age: '28' } }
        #
        #  hash.deep_transform_keys{ |key| key.to_s.upcase }
        #  # => {"PERSON"=>{"NAME"=>"Rob", "AGE"=>"28"}}
        def deep_transform_keys(&block)
          _deep_transform_keys_in_object(self, &block)
        end

        # Destructively converts all keys by using the block operation.
        # This includes the keys from the root hash and from all
        # nested hashes and arrays.
        def deep_transform_keys!(&block)
          _deep_transform_keys_in_object!(self, &block)
        end

        # Returns a new hash with all keys converted to strings.
        # This includes the keys from the root hash and from all
        # nested hashes and arrays.
        #
        #   hash = { person: { name: 'Rob', age: '28' } }
        #
        #   hash.deep_stringify_keys
        #   # => {"person"=>{"name"=>"Rob", "age"=>"28"}}
        def deep_stringify_keys
          deep_transform_keys(&:to_s)
        end

        # Destructively converts all keys to strings.
        # This includes the keys from the root hash and from all
        # nested hashes and arrays.
        def deep_stringify_keys!
          deep_transform_keys!(&:to_s)
        end

        # Returns a new hash with all keys converted to symbols, as long as
        # they respond to +to_sym+. This includes the keys from the root hash
        # and from all nested hashes and arrays.
        #
        #   hash = { 'person' => { 'name' => 'Rob', 'age' => '28' } }
        #
        #   hash.deep_symbolize_keys
        #   # => {:person=>{:name=>"Rob", :age=>"28"}}
        def deep_symbolize_keys
          deep_transform_keys{ |key| key.to_sym rescue key }
        end

        # Destructively converts all keys to symbols, as long as they respond
        # to +to_sym+. This includes the keys from the root hash and from all
        # nested hashes and arrays.
        def deep_symbolize_keys!
          deep_transform_keys!{ |key| key.to_sym rescue key }
        end

        private
          # support methods for deep transforming nested hashes and arrays
          def _deep_transform_keys_in_object(object, &block)
            case object
            when Hash
              object.each_with_object({}) do |(key, value), result|
                result[yield(key)] = _deep_transform_keys_in_object(value, &block)
              end
            when Array
              object.map {|e| _deep_transform_keys_in_object(e, &block) }
            else
              object
            end
          end

          def _deep_transform_keys_in_object!(object, &block)
            case object
            when Hash
              object.keys.each do |key|
                value = object.delete(key)
                object[yield(key)] = _deep_transform_keys_in_object!(value, &block)
              end
              object
            when Array
              object.map! {|e| _deep_transform_keys_in_object!(e, &block)}
            else
              object
            end
          end
      end

      using self unless {}.respond_to? :transform_keys

      def self.deep_symbolize_keys(hash)
        hash.deep_symbolize_keys
      end
    end
  end
end
